Major manufacturing plants, large cities, irrigation systems and power generation facilities require large quantities of water for their successful operation. For reasons of economy and to facilitate inspection, it is desirable that the length of the collection pipe which must be placed in a body of water such as a lake or a river be minimized. It is also desirable that the screen assembly which filters the water entering the collection pipe be of as small a size as possible. Still more important, however, is the necessity of protecting fish and other aquatic organisms from harm and preventing buildup of debris along the length of the screen by ensuring that the maximum peak flow velocity through any of the slots of the intake screen is kept at 0.5 feet per second or below. One prior art flow modifier comprises a single pipe which extends within a screen cylinder. The single pipe flow modifier is typically 50% of the diameter of the screen cylinder and about 33% of its length. This prior art arrangement is able to increase the flow uniformity, which is the ratio of the average to peak flows, to about 72% as compared to just 32% for a cylinder without a flow modifier.